Recirculating-type liquid coating or paint systems are in widespread commercial use for keeping heavily-bodied pigments uniformly suspended in the liquid paint, assuring thereby uniformity in the color and quality of the paint film applied to a substrate. Such circulating paint systems conventionally comprise a mixing tank equipped with suitable agitation for maintaining the paint uniformly mixed and a pump for transferring the liquid paint under the desired pressure to an automatic or manual spray nozzle. A suitable return line is provided for returning the excess paint back to the mixing tank. At the juncture of the pressurized paint supply line and the spray nozzle, a suitable flow control device is mounted for regulating the amount and pressure of paint in the recirculating system to be supplied directly to the nozzle.
Various flow control devices or paint restrictors have heretofore been used or proposed for use including diaphragm-type regulators, for controlling the flow rate of the paint supply to the spray nozzle. Unfortunately, such prior art constructions of flow regulators have been handicapped by their tendency to become progressively plugged over periods of use, necessitating frequent replacement and/or down time to permit cleaning to restore them to proper operating conditions. The build-up of deposits in such flow regulators causes a progressive decrease in the pressure of the liquid coating composition supplied to the nozzle, whereby variations in the quality and thickness of the coating occurs, also detracting from their use.
The flow control device of the present invention overcomes many of the problems and disadvantages associated with prior art structures, providing a simple, economical and durable device which can be directly connected to the fluid inlet of a conventional spray gun and is readily adjustable to provide the desired pressure and flow rate of liquid coating compositions over prolonged time periods without incurring any significant plugging or variation in the preset flow pattern.